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Ann. Geophys., 24, 3313-3327, 2006
www.ann-geophys.net/24/3313/2006/
© European Geosciences Union 2006
Sun-Earth System Interaction studies over Vietnam: an international cooperative project
C. Amory-Mazaudier1, M. Le Huy2, Y. Cohen3, V. Doumbia4,*, A. Bourdillon5, R. Fleury6, B. Fontaine7, C. Ha Duyen2, A. Kobea4, P. Laroche8, P. Lassudrie-Duchesne6, H. Le Viet2, T. Le Truong2, H. Luu Viet2, M. Menvielle1, T. Nguyen Chien2, A. Nguyen Xuan2, F. Ouattara9, M. Petitdidier1, H. Pham Thi Thu2, T. Pham Xuan2, N. Philippon**, L. Tran Thi2, H. Vu Thien10, and P. Vila1
1CETP/CNRS, 4 Avenue de Neptune, 94107 Saint-Maur-des-Fossés, France
2Institute of Geophysics, Vietnamese Academy of Science and Technology , 18 Hoang Quoc Viet, Cau Giay, Hanoï, Vietnam
3IPGP, 4 Avenue de Neptune, 94107 Saint-Maur-des-Fossés, France
4Laboratoire de Physique de l'Atmosphère, Université d'Abidjan Cocody 22 B.P. 582, Abidjan 22, Côte d'Ivoire
5Institut d'Electronique et de Télécommunications, Université de Rennes Bât 11D, Campus Beaulieu, 35042 Rennes, cédex, France
6ENST, Université de Bretagne Occidentale, CS 83818, 29288 Brest, cédex 3, France
7CRC , Faculté des Sciences, 6 Boulevard Gabriel, F 21004 Dijon cédex 04, France
8Unité de Recherche Environnement Atmosphérique, ONERA, 92332 Chatillon, cédex, France
9University of Koudougou, Burkina Faso
10Laboratoire signaux et systèmes, CNAM, 292 Rue saint Martin, 75141 Paris cédex 03, France
*V. Doumbia previously signed V. Doumouya
**affiliation unknown
Abstract. During many past decades, scientists from various countries have studied
separately the atmospheric motions in the lower atmosphere, in the Earth's magnetic
field, in the magnetospheric currents, etc. All of these separate studies lead
today to the global study of the Sun and Earth connections, and as a
consequence, new scientific programs (IHY- International Heliophysical Year,
CAWSES- Climate and Weather in the Sun-Earth System) are defined, in order to
assume this new challenge. In the past, many scientists did not have the
possibility to collect data at the same time in the various latitude and
longitude sectors. Now, with the progress of geophysical sciences in many
developing countries, it is possible to have access to worldwide data sets.
This paper presents the particularities of geophysical parameters measured by
the Vietnamese instrument networks. It introduces a cooperative
Vietnamese-IGRGEA (International Geophysical Research Group Europe Africa)
project, and presents, for the first time, to the international community, the
geophysical context of Vietnam.
Concerning the ionosphere: since 1963, during four solar cycles, the
ionosonde at Phu Thuy (North Vietnam) was operating. The Phu Thuy data exhibits the
common features for the ionospheric parameters, previously observed in other
longitude and latitude sectors. The critical frequencies of the E, F1 and F2
ionospheric layers follow the variation of the sunspot cycle. F2 and E
critical frequencies also exhibit an annual variation. The first maps of TEC
made with data from GPS receivers recently installed in Vietnam illustrate
the regional equatorial pattern, i.e. two maxima of electronic density at
15° N and 15° S from the magnetic equator and a trough of
density at the magnetic equator. These features illustrate the equatorial
fountain effect.
Concerning the Earth's magnetic field: a strong amplitude of the equatorial
electrojet was first observed by the CHAMP satellite at the height of 400 km
in the Vietnamese longitude sector. In this paper we compare the ground
magnetic observations of the Indian and Vietnamese magnetometer networks.
This comparison highlights the regional structure of the amplitude of the
equatorial electrojet, which is stronger in Vietnam than in India.
Concerning the monsoon: Vietnam exhibits a strong monsoon and has mainly
one rainy season peaking in August, hence associated with the southwest
monsoon flow. But some monsoon variability from one place to another is
related to the orography. In the mountainous northern regions of Vietnam,
there is an "early" monsoon peaking in July. In the coastal regions between
12° N and 19° N the monsoon season is centered on October.
Concerning lightning: Vietnam is a country of strong atmospheric storms
with some areas of very intense lightning in North Vietnam (22,5° N,
105° E) and in South Vietnam (11° N, 107° E). In North Vietnam
strong lightning is associated with the most intense rainy region.
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